Security key refresh for dual connectivity

Abstract

Embodiments have a master eNB with a control plane and optional data plane to user equipment and a secondary eNB with a data plane to the user equipment. The user equipment thus uses both the master eNB and the secondary eNB for data communications while receiving control information from only the master eNB. The master eNB and secondary eNB are connected with an X2 interface. When the secondary eNB desires to refresh its security key, it informs the master eNB using the X2 interface. The master eNB then uses its control plane with the user equipment to initiate a security key refresh for the secondary eNB.

What is claimed is: 
     
       1. A method performed by a first base station, comprising:
 receiving, from a second base station, a request to refresh a security key used by the second base station; 
 sending, to a user equipment (UE) that is connected to the first base station and the second base station simultaneously through Dual Connectivity (DC), a radio resource control (RRC) signaling to the UE to effectuate a security key refresh corresponding to the second base station; and 
 receiving, from the UE, a message indicating that the security key refresh has been completed. 
 
     
     
       2. The method of  claim 1 , wherein the first base station is a primary master base station and the second base station is a secondary base station in the DC. 
     
     
       3. The method of  claim 1 , wherein the request to refresh the security key is received before Packet Data Convergence Protocol (PDCP) count for a bearer is about to wrap around. 
     
     
       4. The method of  claim 1 , wherein the RRC signaling to the UE to effectuate the security key refresh is an RRCConnectionReconfiguration message, and the message indicating that the security key refresh has been completed is an RRCConnectionReconfigurationComplete message. 
     
     
       5. The method of  claim 1 , wherein security key refresh information communicated to the UE causes the UE to derive a new security key used to communicate with the second base station. 
     
     
       6. The method of  claim 1 , further comprising:
 sending, to the second base station, a security key refresh acknowledgement message. 
 
     
     
       7. The method of  claim 6 , wherein only the first base station has a control plane in the UE. 
     
     
       8. The method of  claim 6 , wherein the security key refresh acknowledgement message comprises a timing reference from which the second base station should begin using the security key that has been refreshed. 
     
     
       9. An apparatus comprising:
 one or more hardware processors, configured to cause a user equipment (UE) to:
 receive a control message from a first base station to refresh a security key used to communicate with a second base station, wherein the control message is sent by the first base station in response to the second base station sending a request to refresh the security key to the first base station, wherein the UE is connected to the first and the second base stations simultaneously through Dual Connectivity (DC); 
 derive a new security key used by the UE to communicate with the second base station; and 
 send a message indicating that a refresh for the security key has been completed. 
 
 
     
     
       10. The apparatus of  claim 9 , wherein the first base station is a primary master base station and the second base station is a secondary base station in the DC. 
     
     
       11. The apparatus of  claim 9 , wherein the first base station is configured to send a security key refresh acknowledgement message to the second base station, wherein the security key refresh acknowledgement message comprises information used by the second base station to derive the new security key. 
     
     
       12. The apparatus of  claim 9 , wherein the control message to refresh the security key is an RRCConnectionReconfiguration message, and the message indicating that the refresh for the security key has been completed is an RRCConnectionReconfigurationComplete message. 
     
     
       13. The apparatus of  claim 9 , wherein the request to refresh the security key is received by the first base station before Packet Data Convergence Protocol (PDCP) count for a bearer is about to wrap around. 
     
     
       14. The apparatus of  claim 9 , wherein only the first base station has a control plane in the UE. 
     
     
       15. A user equipment (UE), comprising:
 transceiver circuitry; and 
 one or more processors coupled to the transceiver circuitry, wherein the one or more processors are configured to cause the UE to:
 receive a control message from a first base station to refresh a security key used to communicate with a second base station, wherein the control message is sent by the first base station in response to the second base station sending a request to refresh the security key to the first base station, wherein the UE is connected to the first and the second base stations simultaneously through Dual Connectivity (DC); 
 derive a new security key used by the UE to communicate with the second base station; and 
 send a message indicating that a refresh for the security key has been completed. 
 
 
     
     
       16. The UE of  claim 15 , wherein the first base station is a primary master base station and the second base station is a secondary base station in the DC. 
     
     
       17. The UE of  claim 15 , wherein the first base station is configured to send a security key refresh acknowledgement message to the second base station, wherein the security key refresh acknowledgement message comprises information used by the second base station to derive the new security key. 
     
     
       18. The UE of  claim 15 , wherein the control message to refresh the security key is an RRCConnectionReconfiguration message, and the message indicating that the refresh for the security key has been completed is an RRCConnectionReconfigurationComplete message. 
     
     
       19. The UE of  claim 15 , wherein the request to refresh the security key is received by the first base station before Packet Data Convergence Protocol (PDCP) count for a bearer is about to wrap around. 
     
     
       20. The UE of  claim 15 , wherein only the first base station has a control plane in the UE.